This is a collaborative research effort of Northwestern University and the University of California, Los Angeles to evaluate common and specific risk factors for anxiety disorders and depression. Each site will work a common protocol. We propose a prospective longitudinal study of 700 high school juniors, recruited in two cohorts over consecutive years at two high schools (Evanston and Santa Monica). Using a high-risk design, participants at high risk (according to Neuroticism scores) will be oversampled relative to medium and low risk groups. Their progression will be carefully tracked over the course of 8 to 10 assessments staggered over four to four and a half years of data collection. The participant sample will be geographically, ethnically, and socio-economically diverse. The proposal takes a comprehensive biopsychosocial approach to the conceptualization and measurement of risk factors, which include Neuroticism, depressogenic cognitive style, anxiety sensitivity, introversion and low positive affectivity, sociotropy and autonomy. Measures will include self report, parental report, as well as information processing tasks (modified Stroop, memory tasks), affective modulation of startle reactivity, and ambulatory cortisol assays. In addition, diathesis-stress interactions will be evaluated on the basis of contextual assessment of chronic and episodic life stress. Outcome will be measured in terms of symptoms and diagnosis of anxiety and depression. Various models of commonalities and specificities of risk and their interaction with stress will be tested using hierarchical logistic regression and structural equation modeling. The findings may further our conceptualization of emotional disorders and provide the platform for prevention research.